1) Field of the Invention
The present invention relates to a stereoscopic optical system, and an optical apparatus for stereoscopic measurement, a stereoscopic measurement apparatus and a stereoscopic observation apparatus each using the stereoscopic optical system.
2) Description of Related Art
There grows a request for quantitatively understanding measurement objects such as damages and losses inside machines and affected parts of human bodies. As a technique to measure a measurement object such as a damage or loss or an affected part, there is known the stereoscopic measurement in which an identical point is imaged in two directions involving a parallax, a displacement between corresponding measurement points on the respective images is obtained by a correlation operation between captured images, and the size or depth of the object is measured from the obtained displacement using the principle of triangulation.
Conventionally, as optical systems for capturing images involving a parallax, those recited in, for example, Japanese Patent Kokai No. Hei 08-122665, Japanese Patent Kokai No. 2003-5096, Japanese Patent Kokai No. Hei 11-6967, Japanese Patent Kokai No. Hei 08-234117, and Japanese Patent Kokai No. Hei 07-261099 have been proposed.
The optical system recited in JP Kokai No. Hei 08-122665 is provided at the distal end of the insertion part of an endoscope, and has, for example, an objective optical system 53 composed of negative lenses 51L and 51R arranged side by side and an axially symmetric positive lens unit 52, and two image sensors 54L and 54R arranged side by side, as shown in FIG. 1. In FIG. 1, the reference symbols 52R and 52L denote apertures of diaphragms provided in the positive lens unit 52. It is configured so that optical images 55L and 55R involving a parallax are formed on image pickup surfaces of the image sensors 54L and 54R, upon two paths of rays being formed via the objective optical system 53.
The optical system recited in JP Kokai No. 2003-5096 is used in an endoscope system that includes an objective optical system for conducting measurement or stereoscopic viewing, and is composed of, for example, a first unit 60 with a negative power having two sets of lenses 60L and 60R arranged side by side, a second unit 61 with a positive power, a third unit 62 with a positive power, and an image capture unit 63 including one image sensor 63a, as shown in FIG. 2. It is configured so that two images involving a parallax are formed on that one image sensor 63a via the first unit 60 through the third unit 62.
The optical system recited in JP Kokai No. Hei 11-6967 is provided at the distal end of the insertion part of an endoscope, and has, for example, an objective optical system 74 composed of a pair of negative lenses 71L and 71R, a pair of positive lenses 72L and 72R and one positive lens unit 73, and one image sensor 75, as shown in FIG. 3. It is configured so that two images involving a parallax are formed on that one image sensor 75.
The optical system recited in JP Hei 08-234117 is used in a stereoscopic rigid endoscope, and is composed of, for example, in order from a position of a final image In formed by a relay lens system (not shown), which defines one optical axis and includes at least one relay lens, rearwards, a pupil dividing means 81 arranged in the vicinity of a pupil position, an image forming optical system 82, and one image sensor 83, as shown in FIG. 4A. For the pupil dividing means 81, for example, a rotary disc shown in FIG. 4B having an aperture 81a or a liquid crystal shutter shown in FIG. 4C in which the position of its aperture 81a (81b) is changed is used. It is configured so that two images obtained by pupil division in a time-division manner via the pupil dividing means 81 are captured by the image sensor 83.
The optical system recited in JP Kokai No. Hei 07-261099 is used in a stereoscopic endoscope, and has, for example, an objective optical system 91, relay lens systems 92a, 92b and 92c, a pupil dividing image forming means 93, and image sensors 94R and 94L provided in the grip section of the endoscope, as shown in FIG. 5A. The objective optical system 91 is composed of a pair of front group optical systems 911R and 911L arranged in parallel with their optical axes being spaced away by a predetermined distance d and a rear group optical system 912 arranged along a single optical axis, and forms two images 95R and 95L involving a parallax at positions substantially spatially coinciding with each other. The relay optical systems 92a, 92b and 92c are serially arranged to have a common optical axis, and relay the images 95R and 95L at the equal magnification. The pupil dividing image forming means 93 is composed of a pupil image forming lens system 93a, mirror sections 93bR and 93bL, and image forming lens systems 93cR and 93cL. The pupil image forming lens system 93a forms images of two pupils, which are conducted by the relay lens systems 92a, 92b and 92c, of the objective optical system 91 at positions spatially separated from each other. The mirror sections 93bR and 93bL parallel shift two bundles of rays from the two pupils of the objective optical system 91 away from each other. The image forming lens systems 93cR and 93cL are configured to form images 96R and 96L on the image sensors 94R and 94L, respectively.
Also, the optical system recited in JP Kokai No. Hei 07-261099 is configured so that, for example, another occurrence of relay is made on the image side of the relay lens system 92c, by a pupil image forming lens system 93a′ and an image forming lens system 93c′ that are arranged on the same optical axis as the relay lens system 92c, as shown in FIG. 5B. The relayed images 96R and 96L are formed at a substantially same position, to be captured by an image sensor 94′. A shutter 97 is arranged between the pupil image forming lens system 93a′ and the image forming lens system 93c′, to intercept the bundles of rays alternately so that two images are not simultaneously formed on the image sensor 94′.